Species Composition of the Seed Bank in the Estuarine Part of the Il’d’ River and Neighboring Areas

The plant communities of riparian area, or cyclically flooding zone of the water reservoir depend on the diaspores accumulated in the ground and seed banks. Dramatic changes of habitat conditions of plants require the availability a wide ecological spectrum of species in the soil seed bank, from hydrophytes to mesophytes. The seed bank of the estuary region of the Il’d’ River and neighboring areas consists of 44 plant species, including 38 species found in the mouth of the tributary and 20, in the approach channel. Most of the discovered species are typical to the study region and are found either on the shore or in the immediate vicinity of the river. Coastal plants that entered water represent the dominant (54%) ecological group in the seed bank. The observed patterns are similar for most stations. The proportion of hydrophytes at the vast majority of stations is low (15%), although at some stations (in the transition zone of the receiver) it reaches 23%. No hydrophytes have been found in the seed banks of the free flow and transition zones of the tributary. The floral diversity in the estuarine area is not evenly distributed; it increases with distance from the tributary. The level of floral similarity changes in a similar way, reaching a maximum of 41% in the transition zone of the receiver. Although Betula pendula , Chenopodium album , and Phalaroides arundinacea (R-strategy species) are found in all the studied zones, most species tend to certain areas of the estuarine region.